Variable displacement mechanism

ABSTRACT

A variable displacement mechanism for use as a prime mover, pump or compressor having a frame supporting a pair of cylinder barrels for rotation about their common respective axes which can be varied from 90* to 180* with respect to each other, each cylinder barrel including a plurality of equally angularly and radially spaced cylinders having pistons therein which are interconnected through pivotal connectors with corresponding pistons of the other cylinder barrel to permit reciprocating motion of the pistons and transfer or torque between these pistons and the rotatable cylinder barrels during rotation and between the rotating cylinder barrels and a shaft fixed to one of the cylinder barrels.

United States Patent Fox [54] VARIABLE DISPLACEMENT MECHANISM [72]Inventor: Robert M. Fox, Warren, Mich.

[73] Assignee: General Motors Corporation, Detroit,

Mich.

[22] Filed: Nov. 9, 1970 [21] Appl.No.: 88,062

[52] U.S.Cl ..9l/500,91/504,91/505 [51] lnt.Cl ..F0lb 13/04 [58] FieldolSearch ..91/500,504,505;92/60.5; 417/274 [56] I References CitedUNITED STATES PATENTS 1,943,664 1/1934 Fear ..91/500 1,986,584 1/1935Koplar.....

MacNeil is] 3,656,408 [451 Apr. 18, 1972 2,967,395 1/1961 Foerster..60/53 A 2,971,498 2/1961 Bloch ..417/222 3,142,963 8/ 1964 Thoma..60/52 Primary Examiner-William L. Freeh Attorney-Jean L. Carpenter andArthur N. Krein [5 7] ABSTRACT A variable displacement mechanism for useas a prime mover, pump or compressor having a frame supporting a pair ofcylinder barrels for rotation about their common respective axes whichcan be varied from 90 to 180 with respect to each other, each cylinderbarrel including a plurality of equally an 8 Claims, 8 Drawing FiguresFATE NTEDAPR 18 1972 SHEET 1 BF 3 INVEN'I 1R, BY fider/Wfi v ATTORNEYPATENTEDAPR 18 I972 3,656,408 sum 2 or s ATTORNEY RATIO COMPRESSIONPATENTEIJIPII 18 I972 v 3,656,408 SHEET 30F 3 STROKE P3 (O=I.5c)

| l l O I l I I l 2 3 4 STROKE INCHES I I l I l I O l I I I I I 5 IO 2oso 4o ROTATION ANGLE o OEOREEs COMPRESSION RATIO CHARACTERISTICSINVENIOR.

ATTORNEY 1: LE DISPLACEMENT MECHANISM This invention relates to avariable displacement mechanism for use as a prime mover, pump orcompressor and, in particular, to a variable displacement harmonicmechanism wherein displacement can be varied while the mechanism is inoperation and in the case of a prime mover, a constant compression ratiocan be maintained while varying the displacement of the mechanism.

Various arrangements have been used in the prior art to utilize, asprime movers, pumps or compressors, structures in which one or morecylinder barrels are interconnected to rotate about their respectiveaxes of rotation and are provided with a plurality of cylinders arrangedin each cylinder barrel concentrically about and parallel to its axis ofrotation. However, none of the known prior art structures were capableof operation as variable displacement mechanisms operable, if

desired, at a constant compression ratio as its displacement could bevaried.

Accordingly, it is the principal object of this invention to improve areciprocating type mechanism for use as a variable displacement harmonicmechanism in which a pair of rotatable cylinder barrels having pistonsoperating in cylinders arranged concentrically about and parallel to theaxis of rotation of their respective cylinder barrels are pivotallyconnected together so that as the bank angle between cylinder barrels isvaried, the output of the mechanism is varied while maintaining constantor varied compression ratios in the cylinders, as desired. 7

Another object of this invention is to provide a compact, lightweight,low cost, variable displacement mechanism of simplified design.

These and other objects of the invention are obtained by means of avariable displacement mechanism having a frame supporting a pair ofrotatable cylinder barrels on axes intersecting each other at anglesvarying from 90 to 180 with respect to each other. Each cylinder barrelincludes annularly spaced cylinders having pistons which areinterconnected through pivotal connecting pins with correspondingpistons of the other cylinder barrel. This provides for reciprocatingmotion of the pistons and the transfer of torque from the rotatablebarrels and from a drive shaft connected to the inner end of one of thecylinder barrels. Each cylinder barrel cooperates with a nonrotatablehead fixed to the frame of the mechanism adjacent to the cylinder barrelwith which it cooperates with intake and discharge ports therein placedsequentially into communication with the spaced cylinders as thecylinder barrel rotates relative to the nonrotatable head.

For a better understanding of the invention, as well as other objectsand further features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a perspective view of the variable displacement mechanism ofthe invention;

FIG. 2 is a sectional view of one of the cylinder barrels of themechanism of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is a sectional view of the variable displacement mechanism ofFIG. 1 with the axes of rotation of the cylinder barrels normal to eachother;

FIG. 6 is a view similar to FIG. 5 but with the axes of rotation of thecylinder barrels positioned at an angle greater than 90 but less than180 with respect to each other;

FIG. 7 is a view illustrating how the pivotal axis between the twocylinder barrels can be varied relative to the axis of rotation of thecylinder barrels; and,

FIG. 8 is a plot of compression ratio versus stroke and angle settingfor different placements of the pivotal axis between the cylinderbarrels illustrating how a constant compression ratio or variablecompression ratios can be obtained by varying the location of thepivotal axis.

For purposes of this disclosure, the invention is illustrated anddescribed as it relates to a compressor. However, it should be realizedthat the structure and principles discussed herein are equallyapplicable for use in a pump or prime mover and, specifically, thedisclosure relating to compression ratios is especially applicable to aprime mover.

Referring now to FIGS. 1, 2, 5 and 6, there is shown a variabledisplacement compressor having a pair of cylinder barrels 10 and 11joumaled in cylinder support frames 12 and 13, respectively, forrotation with their axes of rotation in a common plane, the cylindersupport frames being pivotally connected together with one of thecylinder support frames movable with respect to the other for varyingthe angle of intersection of the axes of rotation of the two cylinderbarrels.

As shown in FIG. 1, each of the support frames 12 and 13 issubstantially U-shaped with one leg 14 thereof supporting a cylinderhead 15 fixed thereto in a suitable manner and the other leg 16, in theform of a ring, having a bearing 17 mounted therein to rotatably supportone end of a cylinder barrel. Support frames 12 and 13 are provided withapertured flanges l8 and 19, respectively, to receive the pivot member21 whereby the support frames, and therefore the cylinder barrels, canbe pivoted with respect to each other about the axis of the pivotmember. A displacement actuating mechanism 22, which may be a doubleacting hydraulic cylinder or the like, is operatively connected byconduits 23 to a source of pressurized operating fluid, not shown, andis pivotally connected at opposite ends by a clevice 24 and pin 25arrangement to flanges 26 on each of the support frames 12 and 13. Inaddition, one of the support frames, support frame 12 in the embodimentshown, is provided with depending brackets 27 whereby it can be mountedto a suitable mounting platform which may, for example, also carry thedrive motor, not shown, to drive the compressor.

Cylinder barrel 10 is supported in support frame 12 for rotation bymeans of the bearing 17 and by a shaft 31 which is joumaled in bearing32 positioned in the cylinder head 15 associated with this cylinderbarrel. As shown, shaft 31 extends through a central counterbore 33 inthe cylinder barrel 10 and is fixed for rotation therewith by means of akey 34. Shaft 31 is held axially with respect to the cylinder head 15 bya shoulder 31a on the shaft and by means of a retaining ring 35positioned in a suitable groove formed for this purpose in the shaft 31,with the free end of the shaft extending through a suitable aperture inleg 14 and having a pulley 36 fixed thereto whereby this shaft can becoupled by a belt 37 to a suitable drive motor, not shown. Cylinderbarrel 10 is biased into sliding sealing engagement with its associatedcylinder head 15 by means of a coiled spring 38 encircling shaft 31 withone end thereof abutting against the cylinder barrel 10 and the otherend abutting against a spring retainer collar 41 held in place by aretaining ring 42 positioned in a suitable groove in the shaft 31.

In a similar manner, cylinder barrel 11 is rotatably supported in thesupport frame 13 by means of a bearing 17 and by a stub shaft 43joumaled in a bearing 32 positioned in the cylinder head 15 associatedwith this cylinder barrel. Cylinder barrel 11 is biased into slidingsealing engagement with its associated cylinder head 15 in the samemanner as described above with respect to cylinder barrel 10.

Radially spaced outward from the central axis of the cylinder barrels 10and 11 are a plurality of cylinders 44, six in the embodiment shown,equallyspaced apart circumferentially one from the other, with the axesof the cylinders in a cylinder barrel being parallel with the centralaxis of that cylinder barrel. The cylinders 44 of cylinder barrel l0slidably receive pistons 45 while the cylinders 44 of cylinder barrel 11slidably receive pistons 46. The number one piston 45 in cylinder barrel10 is connected by a pivot pin 47 to the number one piston 46 incylinder barrel 11. The remaining pistons 45 in cylinder barrel 10 aresimilarly connected to the remaining pistons 46 in cylinder barrel 11.The connecting piston pivot pins 47 rotate with the cylinder barrels,but travel in an elliptical path.

As previously described, cylinder support frame 12 rotatably supportingcylinder barrel 10 is fixed while the cylinder support frame 13rotatably supporting cylinder barrel 11 can be rotated so that the angleof intersection between the axes of the two cylinder barrels can bevaried from 90 to 180. Full piston stroke is obtained at the 90 angleand zero piston stroke at I80". This arrangement provides a variabledisplacement mechanism so that the desired displacement of the pistonswithin the cylinders can be obtained by adjusting the angle between thetwo cylinder barrels to meet the desired output requirement.

The cylinder heads 15 also serve as valve plates controlling the ingressand egress of fluid into and from the cylinders through the arcuateopenings 48 provided in the ends of the cylinder barrels incommunication with the cylinders. As shown in FIGS. 3 and 4, eachcylinder head is provided with an inlet 51 and an outlet 52 in the formof an elongated arcuate slot and a shorter arcuate slot, respectively,extending through the walls of the cylinder head 15. The inlet 51 issuffrciently long to permit communication of a cylinder therewith duringthe entire stroke of the piston within that cylinder, with a number ofcylinders thus being in overlapping communication with the inlet 51. Theoutlet 52 is short enough so that at any given time, only one cylinderis fully in communication with the outlet during the final portion ofthe compression stroke of a piston within that cylinder.

In the embodiment disclosed, inlet and discharge from the two cylinderbarrels is readily provided for by common manifolds conveniently formedas part of the pivot member 21. As shown, the bottom of the pivot memberis provided with an inlet passage 53 in communication with arcuateradial passages 54. A pair of pivotal ring members 55, positionedbetween a shoulder provided near the bottom of the pivot member, and asnap ring 56 each have a radial passage 57 therein and are connected byflanged conduits 61 and 62 to the cylinder heads for the cylinderbarrels and 11, respectively.

In similar manner, outlets 52 in the cylinder heads for the cylinderbarrels 10 and 11 are connected by flanged discharge conduits 63 and 64,respectively, to the radial passages 57 and ring members 55 pivotallymounted with discharge ring 65 near the top of the pivot member 21between a shoulder provided thereon and a snap ring 56 positioned withina suitable groove formed for this purpose in the pivot member 21. Theradial passages 54 in these ring members 55 are in communication viaarcuate radial passages 66 with an axial passage 67 with dischargetherefrom through a radial passage 68 in communication with a radialpassage 71 in the ring member 65.

In the subject de ice, variable displacement is obtained by changing thepiston stroke which can be done while the device is operating. Asdescribed, cylinder barrel 10 and cylinder barrel ll rotate about theaxis of shafts 31 and 43, respectively, which, as shown in FIG. 5,normally intersect at a 90 angle to each other. This angular position ofthe axes of rotation of the two cylinder barrels is controlled in asuitable manner through the displacement actuating mechanism 22. Whenthe intersecting angle is 90, a piston travels through a full strokewhich, in the embodiment disclosed, is equal to S, the distance betweendiametrically opposite cylinders as shown in FIG. 5.

Since the compression ratio of a reciprocating piston-type device isestablished by the design clearance between the cylinder head and thetop of the piston with the piston located at top dead center (TDC) of astroke, the following equation applies:

CR (S C)/C wherein: CR Compression Ratio S Stroke ck fs 1 and the samedevice could be designed for an 8:1 compression ratio by decreasing theTDC clearance to C m m 0.57 "Hill.

A constant compression ratio can be maintained in the subject devicethroughout all angular positions of the two cylinder barrels withrespect to each other by proper positioning of the axis P of pivotmember 21 with respect to the pivotal axis of a piston 46 positionedadjacent to the pivot member 21 with its pivotal axis parallel to theaxis P of the pivot member and on the bank angle bisector line L. Whenthe distance D, as shown in FIG. 7, between these axes equals the topdead center clearance C, as measured with the cylinder barrelsintersecting at a 90 angle, then the clearance C will decrease to zerowhen the cylinder barrels are positioned at 180 with respect to eachother and a constant compression ratio will be maintained for allintermediate angles. The following relationship illustrates that forthis value of D, compression ratio is independent of bank angle.

where:

Sm Maximum piston stroke D Offset distance between frame pivot axis andpiston pivot axis or /2 180 bank angle between cylinder barrels).

The graph in FIG. 8 shows the plot of compression ratio versus strokeand a for a device with a pivot point P1 a distance D of 0.8 inch with Dbeing equal to clearance C. In this case the compression ratio remainsconstant for all bank angles from to In the above arrangement when thebank angle between cylinder barrels is increased to l26.87, as shown inFIG. 6, the stroke of the pistons is reduced to one-half full pistonstroke, or in this example 2.0 inches. When the bank angle is increasedto 180, the piston stroke becomes zero.

To yield a variable compression ratio with varying bank angles, thepivot point can be moved along the bank angle bisector to a point oneither side of pivot point P1. For example, pivot point P2 is located onthe bisector at a distance D= 0.5 C above pivot point P] as seen in FIG.7.

Apply the following relationship again, wherein the clearance at a bankangle of 180 will equal 056 and the compression ratio will decrease withincreasing bank angles as shown by the graph of FIG. 3.

As another example, a pivot point P3 is located on the bank anglebisector at a distance D= 1.56, a point below Pl as seen in FIG. 7. Thecompression ratio equation described above again applies, however, abank angle of 180 cannot be reached since top dead center interferencewill occur. In this example, the compression ratio will increase withincreasing bank angles as shown in the graph of FIG. 3.

As shown in FIG. 8, at a bank angle of 90 (1: 45), the compression ratiois the same for both the variable and the constant compression ratioconditions. From the above description and the curves plotted in FIG. 8,it can readily be seen that a complete family of compression ratiocurves can be established and any decreasing or increasing compressionratios can be obtained.

With this arrangement when used in an internal combustion engine, theoutput of the engine can be varied by changing the bank angle betweencylinder barrels while maintaining a constant compression ratio duringall operating conditions of the engine.

When used as a pump or as a compressor, as described, the advantage ofvariable displacement in these devices is that pumping capacity can bechanged to meet the output demand requirements. Thus, if the subjectvariable displacement mechanism is used as an automotive airconditioning compressor, its output can be varied to meet varied loadrequirements for climatic demand and drive speed fluctuations. inaddition, if the subject mechanism were used for this last mentionedpurpose, it would not require the use of a magietic drive clutch asconventionally used on such automotive air conditioning compressors,since its displacement and therefore its output, becomes zero when thebank angle becomes 180. In addition, the straight line motion of thepistons and their interconnection between the cylinder barrels producesimple harmonic motion of the pistons, thereby reducing piston acceleration and allowing higher operating speeds.

What is claimed is:

1. A variable displacement mechanism including a pair of frame means, acylinder barrel mounted in each of said frame means for rotation aboutan axis, a drive shaft connected to one of said cylinder barrels forrotation therewith about said axis of said cylinder barrel, each of saidcylinder barrels having a plurality of cylinders therein equally spacedconcentrically about and parallel to the axis of rotation of saidcylinder barrel, pistons slidably mounted in said cylinders in saidcylinder barrels with corresponding sets of pistons in said cylinderbarrels being pivotally connected at one end toeach other, said framemeans being pivotally connected together about a pivotal axis with thesaid axis of one of said cylinder barrels intersecting the said axis ofthe other of said cylinder barrels in a common plane, and meansoperatively connected to said frame means for varying the angle ofintersection of said axes of said cylinder barrels from 90 to 180 withrespect to each other.

2. A variable displacement mechanism according to claim ll wherein thepair of said frame means each includes a frame and a cylinder head fixedthereto, one end of said cylinder barrel supported thereby beingpositioned in sliding engagement with said cylinder head on said framemeans, each'of said cylinder heads having a fluid inlet and a fluidoutlet for communication with said cylinders of said cylinder barrelwith which it cooperates.

3. A variable displacement mechanism according to claim 11 wherein saidpivotal axis of said pivotal connection of said frame means ispositioned with respect to the rotational axes of said cylinder barrelsto effect a constant compression ratio of said pistons operating in saidbarrels as the angle of intersection of said axes is varied from 90 to180.

4. A variable displacement mechanism including a frame means, a firstbarrel mounted for rotation about an axis in said frame means, saidfirst barrel having a plurality of cylinders therein equally spacedconcentrically around the axis of rotation of said first barrel, 3piston in each of said cylinders, a second barrel rotatably mounted insaid frame means about an axis normally normal to the axis of rotationof said first barrel, said second barrel having a plurality of cylindersequal in number to the number of cylinders in said first barrel, saidcylinders of said second barrel being equally spaced concentricallyaround the axis of rotation of said second barrel,

means interconnecting each of said pistons in said first barrel to acorresponding piston in said second barrel, a shaft journaled in saidframe means and connected to said first barrel for rotationconcentrically therewith, and means operatively associated with saidbarrels for varying the angle of intersection of the axes of rotation ofsaid barrel from said normal angle to an obtuse angle.

5. A variable displacement mechanism according to claim 4 wherein saidframe means includes a first cylinder head and a second cylinder headfixed relative to and positioned in sliding engagement with said firstbarrel and said second barrel, respectively, said first cylinder headand said second cylinder head each having a fluid inlet and a fluidoutlet positioned for sequential communication with said cylinders ofthe barrel with which it cooperates.

A variable displacement mechanism including a first frame means and asecond frame means, a first barrel including a drive shaft fixed theretomounted in said first frame means for rotation about an axis, said firstbarrel having a plurality of cylinders therein with parallel axescentered on a common circle about the axis of rotation of said firstbarrel, a piston in each of said cylinders, a second barrel mounted insaid second frame means for rotation about an axis, said second barrelhaving a plurality of cylinders therein positioned and equal in numberto that of the said cylinders in said first barrel, a piston in each ofsaid cylinders in said second barrel, means interconnecting each of saidpistons in said first barrel to a respective piston in said secondbarrel, said first frame means and said second frame means beingconnected together for pivotal movement about a common axis with theaxes of rotation of said first barrel and said second barrelintersecting each other in a common plane and, a displacement actuatormechanism operatively connected to said first frame means and saidsecond frame means for changing the angle of intersection of the axes ofrotation of said first barrel and said second barrel from an anglenormal with respect to each other to an obtuse angle.

7. A variable displacement mechanism according to claim 6 wherein saidfirst frame means and said second frame means are connected together forpivotal movement about a common axis positioned with respect to the axesof rotation of said first barrel and said second barrel to permit theangle of intersection of said axes of rotation to be varied between andwhile permitting a constant compression ratio to be maintained with thestroke of said pistons being reduced to zero when the intersection ofsaid axes of rotation is 180 with respect to each other.

d. A variable displacement mechanism according to claim 6 wherein saidfirst frame means includes a first cylinder head fixed relative to saidfirst barrel and in sliding engagement with one end thereof, saidsecondframe means includes a second cylinder head fixed relative to saidsecond barrel in sliding engagement with one end thereof, said firstcylinder head and said second cylinder head each having a fluid inletand a fluid outlet positioned to be sequentially in communication withsaid cylinders of said first barrel and said second barrel,respectively.

1. A variable displacement mechanism including a pair of frame means, acylinder barrel mounted in each of said frame means for rotation aboutan axis, a drive shaft connected to one of said cylinder barrels forrotation therewith about said axis of said cylinder barrel, each of saidcylinder barrels having a plurality of cylinders therein equally spacedconcentrically about and parallel to the axis of rotation of saidcylinder barrel, pistons slidably mounted in said cylinders in saidcylinder barrels with corresponding sets of pistons in said cylinderbarrels being pivotally connected at one end to each other, said framemeans being pivotally connected together about a pivotal axis with thesaid axis of one of said cylinder barrels intersecting the said axis ofthe other of said cylinder barrels in a common plane, and meansoperatively connected to said frame means for varying the angle ofintersection of said axes of said cylinder barrels from 90* to 180* withrespect to each other.
 2. A variable displacement mechanism according toclaim 1 wherein the pair of said frame means each includes a frame and acylinder head fixed thereto, one end of said cylinder barrel supportedthereby being positioned in sliding engagement with said cylinder headon said frame means, each of said cylinder heads having a fluid inletand a fluid outlet for communication with said cylinders of saidcylinder barrel with which it cooperates.
 3. A variable displacementmechanism according to claim 1 wherein said pivotal axis Of said pivotalconnection of said frame means is positioned with respect to therotational axes of said cylinder barrels to effect a constantcompression ratio of said pistons operating in said barrels as the angleof intersection of said axes is varied from 90* to 180*.
 4. A variabledisplacement mechanism including a frame means, a first barrel mountedfor rotation about an axis in said frame means, said first barrel havinga plurality of cylinders therein equally spaced concentrically aroundthe axis of rotation of said first barrel, a piston in each of saidcylinders, a second barrel rotatably mounted in said frame means aboutan axis normally normal to the axis of rotation of said first barrel,said second barrel having a plurality of cylinders equal in number tothe number of cylinders in said first barrel, said cylinders of saidsecond barrel being equally spaced concentrically around the axis ofrotation of said second barrel, means interconnecting each of saidpistons in said first barrel to a corresponding piston in said secondbarrel, a shaft journaled in said frame means and connected to saidfirst barrel for rotation concentrically therewith, and meansoperatively associated with said barrels for varying the angle ofintersection of the axes of rotation of said barrel from said normalangle to an obtuse angle.
 5. A variable displacement mechanism accordingto claim 4 wherein said frame means includes a first cylinder head and asecond cylinder head fixed relative to and positioned in slidingengagement with said first barrel and said second barrel, respectively,said first cylinder head and said second cylinder head each having afluid inlet and a fluid outlet positioned for sequential communicationwith said cylinders of the barrel with which it cooperates.
 6. Avariable displacement mechanism including a first frame means and asecond frame means, a first barrel including a drive shaft fixed theretomounted in said first frame means for rotation about an axis, said firstbarrel having a plurality of cylinders therein with parallel axescentered on a common circle about the axis of rotation of said firstbarrel, a piston in each of said cylinders, a second barrel mounted insaid second frame means for rotation about an axis, said second barrelhaving a plurality of cylinders therein positioned and equal in numberto that of the said cylinders in said first barrel, a piston in each ofsaid cylinders in said second barrel, means interconnecting each of saidpistons in said first barrel to a respective piston in said secondbarrel, said first frame means and said second frame means beingconnected together for pivotal movement about a common axis with theaxes of rotation of said first barrel and said second barrelintersecting each other in a common plane and, a displacement actuatormechanism operatively connected to said first frame means and saidsecond frame means for changing the angle of intersection of the axes ofrotation of said first barrel and said second barrel from an anglenormal with respect to each other to an obtuse angle.
 7. A variabledisplacement mechanism according to claim 6 wherein said first framemeans and said second frame means are connected together for pivotalmovement about a common axis positioned with respect to the axes ofrotation of said first barrel and said second barrel to permit the angleof intersection of said axes of rotation to be varied between 90* and180* while permitting a constant compression ratio to be maintained withthe stroke of said pistons being reduced to zero when the intersectionof said axes of rotation is 180* with respect to each other.
 8. Avariable displacement mechanism according to claim 6 wherein said firstframe means includes a first cylinder head fixed relative to said firstbarrel and in sliding engagement with one end thereof, said second framemeans includes a second cylinder head fixed relative to said secondbarrel in sliding engagement with one end thereof, said first cylinderhead and said second cylinder head each having a fluid inlet and a fluidoutlet positioned to be sequentially in communication with saidcylinders of said first barrel and said second barrel, respectively.